EARLIER this month, Maria Gorokhov and Callie Reiff paused during a busy rehearsal day to explain their stage strategies.

Do learn ballerinas’ names, so you can send notes requesting used toe shoes. Don’t touch the soldiers: some of them get angry and make frightening faces. And do, certainly, have a plan should you get nervous: last year, Ms. Reiff said, she followed her mother’s advice and pictured “my mom and my brother in underwear.”

Ms. Gorokhov, 10, will dance in the New York State Theater Friday when the New York City Ballet opens its annual “Nutcracker” run. She is the first-cast Marie, the ballet’s young heroine (she performed the role last year), and will alternate with Ms. Reiff, who is 9.

The girls have much to remember. But they needn’t fear forgetting the steps George choreographed in 1954. For two months they have rehearsed meticulously with Garielle Whittle, their teacher at the School of American Ballet and the City Ballet’s children’s ballet mistress. A City Ballet dancer from 1969 to 1983, she became ballet mistress in 1983, the year Balanchine died. For 25 years she has been the guardian, down to the tiniest detail, of his marvelous choreography for children.

Paramount among her responsibilities is “The Nutcracker”: One hundred and five children. Seventy-one roles. Twelve angels. Sixteen soldiers. Eight mice. Eight candy canes. Party scene boys and girls (six of each, plus two teenagers). Eight Polichinelles. One bunny. Hundreds of rehearsal hours. Forty-six performances. And only one Ms. Whittle. It begins with the all-important casting session.

SATURDAY, SEPT. 27 “No talking!” Striding into the studio, one of her ever-present bottles of diet soda in hand, Ms. Whittle greeted the hopefuls with a sharp command: “If you’re talking, I won’t use you.”

Silence. The children executed short phrases as she took notes and checked heights. The girls angling to be Marie were easy to spot: all wore their carefully curled hair down. Marie or mouse, the pay is the same: $10 a performance.

Marie Gorokhov and one of last year’s princes, Joshua Shutkind, 12, knew they would reprise their roles. Callie Reiff and her prince, Lance Chantiles-Wertz, 11, were cast on the spot. Callie’s eyes crinkled in shocked delight, yet her face remained composed; there is no stoicism like that of young dancers up for a part, and the children were careful not to rejoice if chosen, or sulk if passed over.

Ms. Whittle makes her final decision.

They saved their reactions for the lounge, which is the farthest their sometimes inappropriately zealous parents are allowed. Squeals, “oh my gods!” and bear hugs greeted them. Save for a few candy cane hopefuls who were deemed too tall, only a handful of auditioners this year were not given a part. That “makes things much easier,” Ms. Whittle said. “You don’t have as many broken hearts.”

SUNDAY, OCT. 5 One Balanchine saying Ms. Whittle often repeats is “Ballet is about behavior.” These early party scene rehearsals were the first time many of these children, some as young as 7, were dancing with members of the opposite sex. As they digested a stream of minute corrections, they were learning more than how to hold their hands the City Ballet way (like the petals of a flower opening, Ms. Whittle told them). They were also learning how to learn, how to respect the past, how to treat a partner.

Ms. Whittle was strict but never mean, deft at maintaining the line between raising her voice and yelling. Jennie Somogyi, a City Ballet principal who played Marie as a child, laughingly described her former teacher as being like a friend, only “you were still afraid of her.”

SATURDAY, NOV. 1 When City Ballet’s ballet master in chief, Peter Martins, first saw Balanchine’s “Nutcracker” in 1967, he said, he was astounded at the complexity — choreographic and emotional — of the children’s roles.

“The angels break my heart every time, especially when I stand in the wings,” he said. “It’s like little autobiographies are sailing right past me. One is a big smile, one is almost crying and sad, one is sort of non-engaged.”

He emphasized that audiences must see real children, not miniature dancers. Lance, with his golden curls and only two years of ballet training, fits the bill. At this solo rehearsal, while he awaited Ms. Whittle’s return from a much-needed break, he repeatedly practiced his crucial mime scene, studiously consulting Ms. Whittle’s notes (written in a “Little Prince” journal, naturally).

Initially overwhelmed by the role, he was practicing at home, even exercising with his father to strengthen key muscles. Lance is far more delicate and vulnerable than Joshua, a strong performer who is princely indeed — and also something of a ham. Once last year he blew air kisses to the audience. A letter of apology, Ms. Whittle said, was promptly sent to Mr. Martins.

THURSDAY, NOV. 20 Eight days to go. Ms. Whittle recently confided in friends that she despaired of things coming together this year — only to be reminded that she despaired every year.

In this last full week she had scheduled marathon sessions. Now it was late afternoon, her nerves were frayed and the second party scene cast was fidgeting, giggling and otherwise acting altogether too much like 7-year-olds.

Ms. Whittle, playing Herr Drosselmeier, was teaching the children “tickling”: waggling their outstretched fingers as they surrounded her in a tight scrum. It seemed she would momentarily be devoured by angelic-looking little hellions: an apt metaphor, really.

She called a five-minute break, smacking her forehead and rolling her eyes as they scampered out.

“I usually have them so over-rehearsed that they’re perfect,” she said, leaning against the piano, diet soda in hand. “This year I don’t know what’s going to happen. I’m going to talk to Peter and just say, ‘Listen, I’ve got some very young kids.’ ”

TUESDAY, NOV. 25 “Nutcracker” performances can get monotonous for City Ballet dancers. The children’s excitement “gives you a boost of energy,” said the corps dancer Ralph Ippolito.

Watching the first joint company and children’s rehearsal, the battle scene between soldiers and mice, his words resonated. On one side of the studio, petrified youngsters; on the other, professional male dancers, lounging nonchalantly— and clearly tickled by their diminutive foes.

In the middle, the ballet mistresses Rosemary Dunleavy and Ms. Whittle sought to impose order. The chaotic scene demands finely calibrated performances (the corps member Matthew Renko sported a bloodied forehead, courtesy of a child’s errant sword). But its playfulness is irresistible, particularly the moment when each mouse picks up two soldiers and carts them, legs kicking, offstage.

Giggling and blushing abounded. But this year’s bunny, Ever Croffoot-Suede, was daunted by her task of pulling the tail of the Mouse King (a swaggering Henry Seth, brandishing a large, scary sword). She dissolved into a brief crying jag. The adults quickly surrounded her in a comforting circle.

“It’s my first ‘Nutcracker,’ ” she whispered. “And I’m very nervous.”

WEDNESDAY, NOV. 26 When Ms. Whittle was offered the post of children’s ballet mistress, her first response was an incredulous refusal. In her years dancing “The Nutcracker” she, like many colleagues, had been too focused on her own performances even to notice the little beings rushing about underfoot. Now she is keyed into these youngsters’ lives — and to a particular swath of Balanchine’s choreography — in a singular way.

At the dress rehearsal, the children’s first onstage, her eyes rarely strayed from her charges, who were bearing up impressively well in the pressured situation: parents in the audience, Mr. Martins towering over them, the adult dancers they dream of becoming swirling about them. Not to mention props, costumes, light cues and that giant tree.

This was but a taste of what it would be like the next night they appeared onstage. And Ms. Whittle wouldn’t be there. But she would be close; in the wings, most likely, calling out counts — and making sure each step was done just as its choreographer intended it should be.